Biology - Principles of Inheritance and Variation Question with Solution | TestHub

Colour blindness is an X-linked recessive disorder.

Genotype of the colour-blind father: $X^{c}Y$

Genotype of the normal mother: $X^C{X}^C$

The daughter receives the $X^c$ chromosome from her father and the $X^C$ chromosome from her mother. Thus, her genotype is $X^C{X}^c$ (carrier).

She marries a normal male, whose genotype is $X^{C}Y$.

The cross between the carrier female ($X^C{X}^c$) and the normal male ($X^{C}Y$) produces the following offspring:

Male children receive their X chromosome from the mother and Y chromosome from the father.

The mother produces two types of eggs: $X^C$ and $X^c$ in equal proportions.

Therefore, the male children will be $X^{C}Y$ (normal) and $X^{c}Y$ (colour-blind) in a $1:1$ ratio.

Hence, $50\%$ of the male children will be colour-blind.

Answer: 50 %